Supervisory control system

ABSTRACT

A supervisory control and self-powered indicating system is provided for controlling the operation of a remote electrically operated device from a control station and for indicating at the control station either the operability of the remote device or the absence of an alarm condition, in which a pair of face-toface diodes are connected in series across the transmission lines at the remote location, with the mid-point between the diodes connected through a third diode and through a condition responsive switch to earth ground. The return connection through earth ground at the control station is made through a relay coil and back-to-back diodes connected in series across the transmission lines at the control station. Telemetry is provided through the opening and closing of the condition responsive switch, with the time that this switch remains in a given condition being monitored by the length of time the switch associated with the relay coil at the control station remains in this given condition. Alternatively, the condition responsive switch changes state in response to a predetermined alarm condition which is indicated by a change of state of the switch associated with the relay at the control station.

United States Patent Banville Dec. 23, 1975 SUPERVISORY CONTROL SYSTEM[57] ABSTRACT [76] I v t J l Eugene B ill 161 H s A supervisory controland self-powered indicating sys- Cumberland, RI, 02908 tem is providedfor controlling the operation of a remote electrically operated devicefrom a control sta- [22] Flled' May 1974 tion and for indicating at thecontrol station either the [21] Appl. NQ; 473,358 operability of theremote device or the absence of an alarm condition, in which a pair offace-to-face diodes are connected in series across the transmissionlines at ESCCII; 340/409; 340/310 R the remote location with the midpoint between the F. of e a e i; r I u e 1 e e I I s e v I e e e s U a ale 0 Same 340/409 310 319 condition responsive switch to earth ground.The re- 0/255 177 239 turn connection through earth ground at thecontrol I station is made through a relay coil and back-to-back [56]References cued diodes connected in series across the transmissionUNITED STATES PATENTS lines at the control station. Telemetry isprovided 3,448,447 6/1969 Tetherow 340/409 R hr gh he opening andclosing of the condition re- 3,566,398 2/1971 Rowell 340/409 R sponsiveswitch, with the time that this switch remains 3,588,891 6/1971 Porter340/409 R in a given condition being monitored by the length of3,604,262 9/1971 Craddock 340/239 R time the Switch associated with therelay i at the g control station remains in this given condition. Alter-337423m 6,1973 wifiiiw iiii:.......::::::1::133: 340/239 R naively, thecondition Switch changes State Primary Examiner-Harold 1. PittsAttorney, Agent, or Firm--William Frederick Werner in response toa-predetermined alarm condition which is indicated by a'change of stateof the switch associated with the relay at the control station.

12 Claims, 2 Drawing Figures I'--------- I'- I 20 i i l I I El; l i l I5o PUMP :I l 30 I I INDICATOR 23 I I I 46 52 l l I I I I I 1 @2675 I l Il7| 'T I I I I I3 I I I MULTI TAP 28 l I RESISTOR 27 5 l I I l I l I I7? I I v17 48 l 40 39 36 l I I l NC 37 ALARM X? l I I i l I l l 78 lEARTH GR I t? EARTH GROUND I I T OUND I I 9.- B& E 1 NLL J I E E A @LLLUS. Patent De.23, 1975 Sheet 1 of2 3,928,848

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Dec. 23, 1975 Sheet 2 of2 3,928,848

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SUPERVISORY CONTROL SYSTEM BACKGROUND OF THE INVENTION This inventionrelates to apparatus for the supervisory control of a remote device andmore particularly to provision of a self-powered indicating systemutilizing the transmission lines between the remote and con trolstations, as a source of power for the indicating system, wherebycontrol of a remote device and indication of its operation are indicatedby signals transmitted back to the control station via earth ground andpairs of diodes across the transmission lines at the remote and controlstations.

In the operation of, for instance, remote valving circuits there is anecessity for monitoring not only the state of the valve, but also toinsure that no unauthorized entry has been made at the remote station.This is particularly true of a remote pumping station in which intrudersmay often either damage or inactivate the equipment unbeknownst to thepersonnel at the control station. Additionally, there is a need not onlyfor an alarm system but also for a system which indicates theoperability of the equipment at the remote station.

As described in US. Pat. No. 2,932,014, issued to J. C. Thoresen on Apr.15, 1960, a supervisory system is illustrated in which a separate powersupply at the remote location provides electrical current across apotentiometer, the wiper arm of which is mechanically connected to avalve such that the potential applied to the center of a choke coilacross the power lines is proportional to the valve position. It is thusthe magnitude of the potential delivered to the center of this chokecoil when delivered back to the control station which provides for theindication of the state of the remote valve. It will be appreciated thatdepending on the distances between the control and remote stations thistype of indicating system relys heavily on the stability of the remotepower supply and the absence of change of any transmission linecondition.

The problems of this type of indicating system are solved by the subjectinvention whose remote circuit derives its power directly from thetransmission lines to the remote location and which in general providesan indication of the state of the remote device or the security of theremote station via the complete interruption or non-interruption of anearth ground connection at the remote location to the operative part ofthe remote indicating circuit.

This binary on/off operation of the subject circuit permits a binaryon/off operation of the indicating or alarm circuit at the controlstation and thus is not amplitude sensitive, or sensitive to changes inthe characteristics of the transmission lines between the control andremote stations.

Power for the remote station transmitting device is derived from twoface-to-face diodes connected in series across the transmission linesinter-connecting the control and remote stations. The voltage at themidpoint of these diodes is applied through a further diode and ancondition responsive switch to earth ground at the remote location. Atthe control station aback-toback pair of diodes is connected in seriesthrough re spective resistors across the same transmission line. Themid-point of these back-to-back diodes is connected through a relay coilto earth ground such that when the condition responsive switch at theremote location is closed, the relay coil at the control station isenergized. In one embodiment, an alarm condition is indicated by anearth ground interruption at the remote location. This can be due tounauthorized access through a door or window at the remote station.Alternatively, any sensed condition at the remote station can betranslated into the amount of time that the earth ground is connected tothe remote circuit via the condition responsive switch. This switchclosing time can be monitored at the control station and correlated withthe sensed condition. Thus, for example, fluid flow at the remotestation can be translated into how much time in a giventime interval,the earth ground is connected and this time can be monitored at thecontrol station. Moreover, a Powder-On indicator can be provided at thecontrol station and in a further embodimom, a voltage compensationcircuit is provided.

SUMMARY OF THE INVENTION A self-powered supervisory control andindicating circuit is thus provided for indicating one ofa variety ofconditions at a remote location.

It is therefore an object of this invention to provide self-poweredsupervisory control and condition indicating apparatus at a remotelocation and control station in which earth ground is used as one of theconducting paths.

It is a further object of this invention to provide a supervisory andcontrol circuit used with remote elec' trical apparatus 'in which boththe operation of the apparatus is indicated at a control station as wellas the absence of an intruder or any alarm condition.

Other features and advantages of the invention will appear from theensuing description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagramillustrating one embodiment of the present invention; and

FIG. 2 is a schematic diagram illustrating a second embodiment of thesubject invention, indicating the use of the subject circuit fortelemetry purposes.

DETAILED DESCRIPTION Referring to FIG. 1, a control station 10 is shownconnected to a remote station 11 via transmission lines 12 and 13. Inone embodiment, remote station 11 may be a pump house remote from thecontrol station 10 and includes a pump 14 or any other electronic orelectromechanical device.

In order to actuate pump 14, an alternating current signal is appliedacross an isolation transformer 15 having output terminals 16 and 171.Transmission line 12 is connected to output terminal 16 through ablocking diode 17 which is shunted by a switch 20 connected in parallelwith the diode 17. Between terminal 16 and 171 are connected in series aresistor 21, a diode 22, a diode 23 and a resistor 24, with themid-point between the diodes being illustrated as a point 25. It will beappreciated that in this configuration, diodes 22 and 23 are in aback-to-back configuration.

Transmission line 13 is connected through a relay coil 26 throughmulti-tap resistor. 27 to output terminal 171 of the isolationtransformer 15. The purpose of the multi-tap resistor 27 is to providefor line impedence matching. Once the line impedence is known, a fixedresistor may be utilized in place of multi-tap resistor 27. Relay coil26 is shunted by a diode 28 to prevent ringing. Relay coil 26 controls anormally open set of contacts which activate an indicator 32 responsiveto the continued energization of relay coil 26. A potentiometer 34 isconnected from transmission line 13 to terminal 171 through resistor 27and the wiper arm of potentiometer 34 for purposes of adjusting thetransmission line potential. Potentiometer 34 is adjusted to preventminute or small amounts of voltage from falsely energizing relay coil26, since the transmisssion lines carrying the electrical current areoften energized or influenced by the proximity of transformers orhighvoltage power lines. Potentiometer 34 is used to prevent suchinduced voltages from energizing relay coil 26. Since the total loopresistance varies, the setting of potentiometer 34 will vary with eachinstallation.

A relay coil 36 is connected between earth ground and mid point 25 withthis relay coil being shunted by a diode 37, to prevent ringing when therelay coil is de-energized. Relay coil 36 actuates a normally closedswitch 39 into an open position so as to deactivate alarm 40 duringnormal operation of the subject systern.

Turning now to the remote station, a pair of face-toface diodes 42 and43 are connected in series between transmission lines 12 and 13. A relaycoil 44 is connected between the transmission line 12 and a midpoint 45between the face-to-face diodes 42, 43. A further diode, diode 46, isconnected between midpoint 45 and earth ground through either switch 47or switch 48. Switch 47, in one embodiment, is acutated by the openingof a door at the remote station such that switch 47 is opened with theopening of the door and is closed with the closing of the door. Openingof the door will sound an alarm at 40 because of the consequentde-energization of coil 36, with the interruption of the earth groundconnection path between the remote and control stations as will bedescribed hereinafter. Switch 48 is a key-activated, pick-proof, switchwhich is manually closed with the turning of its key. This sets up aclosed circuit with the door switch open 47 thus allowing the door to beopened by authorized personnel without setting off the alarm.

Relay coil 44 actutes normally open switch contact 50 to permit power tobe delivered to pump 14. Pump 14, when in operation, mechanically closesswitch 52 which connects relay 44 directly across lines 12 and 13.

In operation, the ac. circuit which includes relay coil 44 is open dueto the blocking action of diode 17 for voltage of one polarity, and theshunting action of diode 42 prevents energization of coil 44 forvoltages of the other polarity. Power from isolation transformer 15 is,however, provided across relay coil 44 when key switch 20 is firstclosed, thus unblocking diode 17. Upon actuation of switch 20, positivehalf cycles of current at terminal 171 are applied through diodes 28 and43 to mid-point 45, and then to relay coil 44 and back through diode 17,still in a blocked state but now by-passed through closed switch 20,pass through closed switch 20 to complete the energization circuit ofrelay coil 44. This is turn actuates switch 50 into a closed positionfor supplying power to pump 14 or some other electromechanical device.When pump 14 is activated, switch 52 closes such that power fromtransmission line 13 is directly coupled to relay coil 26 during normaloperation of the pump.

On the positive half cycle of alternating current from terminal 16 thispositive going voltage is shunted by diode 42 to point 45 from whence itproceeds through diode 46 through either switch 47 or 48, through earth4 ground to relay coil 36, and through this relay coil to mid-point 25.The potential at point 25 is delivered either through diode 22 andresistor 21 to terminal 16 of the isolation transformer or through diode23 and resistor 24 to terminal 171. This action opens the normallyclosed contacts 39 so that alarm 40 is inhibited.

It will be appreciated that upon actuation of pump 14, relay coil 26will be energized for causing indicator 32 to indicate normal operationof the system. Should an intruder cause switch 47 to be opened, relaycoil 36 is de-energized and alarm 40 sounds. In one operativeembodiment, the half-wave rectified voltage at point 45 at the remotestation is at volts while the voltage at point 25 at the control stationis 4 volts. In this manner, the same transformer is utilized to provideboth the power for relay coil 44 and the power for relay coil 36 and thepower for relay coil 26.

Referring to FIG. 2 in another embodiment, the subject system can beused for supervisory control of a valve 60 in a fluid transmission line61 via a valve reversing solonoid 62. The operation of this valvereversing solonoid is similar to that described in aforementioned US.Pat. No. 2,932,014. In this embodiment, in which reference charactersfor elements in FIG. 2 correspond are compared to like elements in FIG.1, an additional switch 63 is provided in line 13 with potentiometer 34,diode 28, relay coil 26, contacts 30 and indicator 32 removed from thecircuit.

Additionally, switch 52 of FIG. 1 is removed from the circuit and arelay coil 64 is provided for the actuation of the valve reversingsolonoid in a direction opposite to that which accompanies theenergizing of relay coil 44. Additionally, a flow meter 65 is interposedin fluid transmission line 61 which repeatedly opens and closes atelemetry switch 66, which replaces switches 47 and 48. Switch 66 isopened and closed at a rate proportional to fluid flow in conduit 61.Switch 39 tracks the opening and closing of switch 66 during normaloperation. The control station is also provided with a cumulative timeindicator 67 which records the amount of time during a predeterminedtime interval that switch 66 is closed. In its most usual form,indicator 67 may take the form of a conventional integrating device.Since switch 66 is closed for a time period proportional to thevolumetric flow in conduit 61, indicator 67 therefore indicates eitherthe flow rate or indirectly the valve position. In this manner, thecircuit of FIG. 2 functions as a telemetry circuit for indicating eithervalve position or fluid flow.

To further describe the operation of the circuit of FIG. 2, switch 20and 63 are connected in parallel with diodes 17 and 68 respectively. Atthe remote station, a pair of relay coils 44 and 64 are connected inparallel with respective diodes 42 and 43. The relay coils may be ofconventional type and are connected to solonoid 62 arranged in onecondition to open valve 60 and in another condition to close valve 60.Relay coil 44 and solonoid 62 thus form one telemetric receiver whilerelay coil 64 and solonoid 62 form another telemetric receiver. I

When it is desired to open valve 60, switch 20 is closed. Then in thosehalf cycles of the alternating voltage in which a positive voltage isapplied to transmission line 13, assuming the diodes to be poled so asto pass current from left to right in the drawing, current will flowthrough diode 68, through diode 43, around diode 42 and through relaycoil 44 and the closed contacts of switch 20.

Relay coil 44 now being energized, its contacts (not shown) close tocause solonoid 62 to assume a position in which valve 60 is open.

In alternate half cycles in which the voltage applied to transmissionline 13 is negative, no current will flow, since current cannot passthrough diode 68 and the latter cannot be bypassed since switch 63 isopen. Furthermore, relay coil 44 is now short circuited by diode 42 sothat this relay would not be energized even if current could flow inthese last mentioned alternate half cycles. In short, during the halfcycles in which the voltage applied to transmission line 13 is negative,relay coil 44 is not energized; but during half cycles in which thevoltage applied to the transmission line 13 is positive, relay coil 44will be energized or de-energized depending solely whether the contactsof switch are closed or open. Relay coil 44 should of course havesufficient shading as not to change its condition, or chatter during theinterval between alternate half cycles of the alternating current whilethe switch is closed. p

If it is desired to move valve 60 to its closed position, switch 63 isclosed. Thereupon during those half cycles in which the voltage appliedto transmission line 12 is positive, current flows through diodes l7 and42, around diode 43, through relay coil 64, through transmission line13, around diode 68, and through the closed contacts of switch 63.

Relay coil 64 now being energized, its contacts (not shown) are closedto cause the electrical solonoid to assume a position which willeffectively close valve 60. In the alternate half cycles in which thevoltage applied to transmission line 12 is negative, no current willflow, even though switch 63 be held closed since current cannot passthrough diode 17 and the latter cannot be bypassed since switch 20 isopen. Furthermore, relay coil 64 is now short circuited by diode 43 sothat this relay coil would not be energized even if current could flowin said alternate half cycles. Thus the operation of valve reversingsolonoid 62 is controlled by the states of switches 20 or 63. The statusof valve 60 is monitored by flow meter 65 so that indicator 67 indicatesa fully open valve during maximum flow through conduit 61 and minimalflow when valve 60 is closed.

Obviously, the telemetry switch 66 can be activated by any one of avariety of sensing systems such that a predetermined condition at theremote station can be monitored through the transmission lines. Thissystem is not sensitive to voltage changes in that it is a timedependentsystem as opposed to an amplitude dependent system as illustrated in theprior art. Additionally, as will be apparent, the solonoid 62 can bereplaced with any device responsive to two different signals forperforming the prescribed function. The diode arrangement is alsobeneficial in eliminating the necessity for expensive choke coils whileat the same time providing the requisite operation of a supervisorysystem. Of course, the diodes may be replaced with any one of a numberof conventional rectifying devices.

What is claimed is: V

l. A supervisory control system for use between a control station 10 anda remote station 11 connected by a pair of transmission lines 12, 13carrying an ac. signal, comprising:

first rectifying means 42, 43 having an output terminal 45, said firstrectifying means being connected across said transmission lines l2, 13at said remote 1 station 11 for generating a rectified signal at saidoutput terminal 45;

an electromechanical device 44 at said remote station connected betweenone of said transmission lines 12 and said output terminal 45;

second rectifying means 17 in said one transmission line 12 at saidcontrol station 10 for blocking positive-going signals from said remotestation coming in on said one line 12;

means 20 for rendering said second rectifying means unblocking;

condition responsive switch means 47, 48 at said remote station 11 forselectively connecting said output terminal 45, to earth ground; and

means at said control station 10, including an earth ground connection78 responsive to the selective connection and disconnection of saidoutput terminal 45 to earth ground at the said remote station 11 forindicating the state of said condition responsive switch means 47, 48. 1

2'. The supervisory control system of claim 1 wherein said indicatingmeans includes a relay coil, back-toback diodes connected in seriesacross said transmission lines at said control station, means forconnecting the mid-point between said back-to-back diodes to one end ofsaid relay coil and means for connecting the other end of said relaycoil to earth ground.

3. The supervisory control system of claim 1 wherein said firstrectifying means includes a pair of face-toface diodes connected inseries across said transmission lines at said remote station, themid-point between said two diodes constituting said output terminal.

4. The supervisory control system of claim 3 wherein said conditionresponsive switch means includes a diode and a switch connected inseries between said output terminal and earth ground.

5. The supervisory control system of claim 4 wherein said switch isopened responsively to a predetermined alarm condition.

6. The supervisory control system of claim 4 further including means atsaid remote station for sensing the magnitude of a predeterminedcondition and for closing said switch means for a time period over apredetermined time interval proportional to the magnitude of saidpredetermined condition, and wherein said indicating means includesmeans at said control station for indicating said time period.

7. The supervisory control system of claim 6 wherein said predeterminedcondition is fluid flow rate.

8. The supervisory control system of claim 1 and further including meansresponsive to current flow in said transmission lines for indicating thepresence of said current flow.

9. The supervisory control system of claim 1 and further including anisolation transformer having a secondary winding connected across saidtransmission lines at said control station, and means for matching theimpedance of said isolation transformer to the impedance of saidtransmission lines.

10. The supervisory control system of claim 9 further includingback-to-back diodes connected across said secondary winding and a relaycoil connected between the mid-point between said back-to-back diodesand earth ground.

11. A system for indicating at a control station an alarm conditionexisting at a remote location wherein said remote location and saidcontrol station are interconnected with a pair of transmission lines,comprising face-to-face diodes connected across said transmission linesat said remote location; alarm condition responsive means at said remotelocation for connecting the mid-point between said face-to-facc diodesto earth ground under normal operating conditions and for disconnectingsaid mid-point responsive to said alarm condition; back-to-back diodesconnected across said transmission lines at said control station; andmeans connected between the mid-point between said backto-back diodesand earth ground for indicating current flow between earth ground andsaid last mentioned mid-point.

; 12. A supervisory control system for use between a control station anda remote station connected by a pair of transmission lines carrying anac. signal, comprising: I

first rectifying means having an output terminal, said first rectifyingmeans being connected across said transmission lines at said remotestation for generating a half-wave rectified signal at said outputterminal;

an electromechanical device at said remote station connected between oneof said transmission lines and said output terminal;

second rectifying means in said one transmission line at said controlstation for blocking positive-going signals from said remote stationcoming in on said one line;

means for rendering said second rectifying means unblocking;

condition responsive switch means at said remote station for selectivelyconnecting said output terminal to earth ground; and

means at said control station for indicating the state of said conditionresponsive switch means, said first rectifying means including a pair offace-to-face diodes connected in series across said transmission linesat said remote station, the mid-point between said two diodesconstituting said output terminal, and further including means connectedbetween said output terminal and the other of said transmission linesfor providing a conducting path around the diode therebetween inresponse to the energization of said electromagnetic device with therendering of said second rectifying means unblocking.

1. A supervisory control system for use between a control station 10 anda remote station 11 connected by a pair of transmission lines 12, 13carrying an a.c. signal, comprising: first rectifying means 42, 43having an output terminal 45, said first rectifying means beingconnected across said transmission lines 12, 13 at said remote station11 for generating a rectified signal at said output terminal 45; anelectromechanical device 44 at said remote station connected between oneof said transmission lines 12 and said output terminal 45; secondrectifying means 17 in said one transmission line 12 at said controlstation 10 for blocking positive-going signals from said remote stationcoming in on said one line 12; means 20 for rendering said secondrectifying means unblocking; condition responsive switch means 47, 48 atsaid remote station 11 for selectively connecting said output terminal45 to earth ground; and means at said control station 10, including anearth ground connection 78 responsive to the selective connection anddisconnection of said output terminal 45 to earth grouNd at the saidremote station 11 for indicating the state of said condition responsiveswitch means 47,
 48. 2. The supervisory control system of claim 1wherein said indicating means includes a relay coil, back-to-back diodesconnected in series across said transmission lines at said controlstation, means for connecting the mid-point between said back-to-backdiodes to one end of said relay coil and means for connecting the otherend of said relay coil to earth ground.
 3. The supervisory controlsystem of claim 1 wherein said first rectifying means includes a pair offace-to-face diodes connected in series across said transmission linesat said remote station, the mid-point between said two diodesconstituting said output terminal.
 4. The supervisory control system ofclaim 3 wherein said condition responsive switch means includes a diodeand a switch connected in series between said output terminal and earthground.
 5. The supervisory control system of claim 4 wherein said switchis opened responsively to a predetermined alarm condition.
 6. Thesupervisory control system of claim 4 further including means at saidremote station for sensing the magnitude of a predetermined conditionand for closing said switch means for a time period over a predeterminedtime interval proportional to the magnitude of said predeterminedcondition, and wherein said indicating means includes means at saidcontrol station for indicating said time period.
 7. The supervisorycontrol system of claim 6 wherein said predetermined condition is fluidflow rate.
 8. The supervisory control system of claim 1 and furtherincluding means responsive to current flow in said transmission linesfor indicating the presence of said current flow.
 9. The supervisorycontrol system of claim 1 and further including an isolation transformerhaving a secondary winding connected across said transmission lines atsaid control station, and means for matching the impedance of saidisolation transformer to the impedance of said transmission lines. 10.The supervisory control system of claim 9 further including back-to-backdiodes connected across said secondary winding and a relay coilconnected between the mid-point between said back-to-back diodes andearth ground.
 11. A system for indicating at a control station an alarmcondition existing at a remote location wherein said remote location andsaid control station are inter-connected with a pair of transmissionlines, comprising face-to-face diodes connected across said transmissionlines at said remote location; alarm condition responsive means at saidremote location for connecting the mid-point between said face-to-facediodes to earth ground under normal operating conditions and fordisconnecting said mid-point responsive to said alarm condition;back-to-back diodes connected across said transmission lines at saidcontrol station; and means connected between the mid-point between saidback-to-back diodes and earth ground for indicating current flow betweenearth ground and said last mentioned mid-point.
 12. A supervisorycontrol system for use between a control station and a remote stationconnected by a pair of transmission lines carrying an a.c. signal,comprising: first rectifying means having an output terminal, said firstrectifying means being connected across said transmission lines at saidremote station for generating a half-wave rectified signal at saidoutput terminal; an electromechanical device at said remote stationconnected between one of said transmission lines and said outputterminal; second rectifying means in said one transmission line at saidcontrol station for blocking positive-going signals from said remotestation coming in on said one line; means for rendering said secondrectifying means unblocking; condition responsive switch means at saidremote station for selectively connecting said output terminal to earthground; and means at said control station for indicating the state ofsaid condition responsive switch means, said first rectifying meansincluding a pair of face-to-face diodes connected in series across saidtransmission lines at said remote station, the mid-point between saidtwo diodes constituting said output terminal, and further includingmeans connected between said output terminal and the other of saidtransmission lines for providing a conducting path around the diodetherebetween in response to the energization of said electromagneticdevice with the rendering of said second rectifying means unblocking.